The present invention relates to a transmission box for a wheeled machine, particularly of the walking type, of the type comprising, disposed at least partially within the box, a motor input shaft driving a drive wheel to actuate at least one drive shaft of at least one wheel of the machine, a clutch mechanism being disposed between the drive wheel and the drive shaft for the wheel of the machine, this clutch mechanism being activated by driving in rotation the drive wheel and deactivated by driving in rotation the drive shaft of the wheel when the motor input shaft is stopped or when the speed of rotation of the drive shaft of the wheel is greater than the speed of rotation of the drive wheel, as well as a wheeled machine provided with such a transmission box.
Transmission boxes of the mentioned type are well known to those skilled in the art as shown in particular by the patent EP 1 198 981. Such boxes include a clutch, so-called automatic, which does not require for its operation a dedicated control member, such as a fork, as is the case in conventional clutches of the type as that described in EP 0 782 820.
Independently of the required clutch mechanism, there is also provided particularly in the case of machines, such as self-propelled lawnmowers with driven rear wheels, to provide each free end of the drive shaft of the wheels, with a mechanism generally with a ratchet or clutch so as to permit, in particular during turning the machine, a free wheel function of one of the wheels of the same pair of wheels of the machine. Each wheel is thus disconnectable from the drive shaft for the wheels as shown in particular in the patent EP 0 298 016. However, as the clutch mechanism is positioned between the output shaft of the gearbox and the assembly of wheels, it is necessary, in order to permit the wheels to turn at different speeds during turns, to provide each wheel with such a mechanism. The result is an increase in cost. Moreover, the presence of a clutch mechanism adjacent the wheels gives rise to premature wear of the mechanism subjected particularly to dirt and projections of ground connected with the proximity to the wheels.
There is also known, from the patent JP 60-188654, a device for transmission with two clutches. In this device, the box is a box with an open rotatable body, driving a drive wheel. This box is disposed between two fixed plates which form ends of the box. Rolling members are inserted between the plates and the body of the box. The result is a particularly complicated structure.